DESCRIPTION (Verbatim from the Applicant's Abstract): Recent studies have emphasized the limitations of conventional coronary arteriography. These limitations include the large intraobserver and interobserver variability that result from subjective visual grading of coronary stenotic lesions. Furthermore, pathologic findings have shown a lack of correlation between the severity of coronary stenosis as estimated from coronary arteriogram and the actual severity of stenotic lesions measured in postmortem hearts. Because of the major limitations of standard coronary arteriography, a functional measure of stenosis severity such as measurement of regional coronary blood flow obtainable during cardiac catheterization is desirable. The blood flow measurement would provide valuable functional information in addition to the anatomical data obtained during routine coronary arteriography. The purpose of this research plan is to develop of a technique for quantification regional coronary blood flow by combining the first pass distribution algorithm with 3-D reconstruction of coronary artery tree and its implementation in the cardiac catheterization laboratory. More specifically, the aims are: (1) Verification of the linear relation between regional myocardial mass and the sum of arterial branch lengths distal to any point in the coronary vascular tree using a swine animal model. (2) Investigation of the hypothesis that normalized regional coronary blood flow measurement can be made utilizing the first pass distribution analysis technique in conjunction with the sum of arterial branch lengths using 3-D reconstruction of coronary artery tree. (3) Investigation of the hypothesis that normalized regional coronary blood flow measurement can be used to assess coronary artery stenosis severity in different size perfusion beds. (4) Implementation of the regional coronary blood flow measurement technique in the cardiac catheterization laboratory for human studies. The results of this research will provide improved physiological methods of quantitating coronary artery stenosis severity in patients. This quantification technique could be used to measure regional myocardial perfusion in patients undergoing standard coronary arteriography.